1. Field of the Invention
The present invention relates to a fuel cell stack.
2. Description of the Related Art
Conventionally, a solid oxide fuel cell (hereinafter, also abbreviated as SOFC) using a solid electrolyte (solid oxide) is known as a fuel cell.
In the SOFC, for example, a fuel cell (power generation cell) provided with a fuel electrode in contact with a fuel gas on one side of a solid electrolyte membrane while provided with an oxidant electrode (air electrode) in contact with an oxidant gas (air) on the other side is used as a power unit. Further, a fuel cell stack having a plurality of power generation cells stacked via interconnectors has been developed in order to obtain a desired voltage.
In general, in this type of fuel cell stack, a problem arises in that the temperature of the power generation cells closer to the center in a stacking direction of the power generation cells becomes higher than that of the power generation cells closer to the ends in the stacking direction of the power generation cells.
In order to solve this problem, a technique has been proposed for supplying cold air to one lateral side close to the center in the stacking direction, while supplying a heat-exchanged hot gas to the ends in the stacking direction of the fuel cell stack (see Patent Literature 1).
[Patent Literature 1] JP-A-2005-5074
3. Problem Addressed by the Invention
Because the above-described conventional technique supplies cold air from one lateral side, the power generation cells closer to the center in the stacking direction of the fuel cell stack cannot be sufficiently cooled. In addition, the above conventional technique cannot sufficiently increase the fuel gas utilization efficiency.